PROJECT SUMMARY: Viral Innovation Core Contemporary research on the neuroscience of addiction utilizes a broad set of genetically encoded tools that can be used to control neuronal excitability, highlight connectivity between neurons that form microcircuits, and report cellular activity states in behaving animals. Viral vectors exploiting the beneficial features of the Adeno- Associated Virus (AAV) backbone have proven invaluable for delivering genetically encoded tools to specific cell types and circuits in the nervous system, and are critical tools used by the addiction neuroscience community at the University of Minnesota (UMN). With the recent investments made in hiring to grow addiction-related research at UMN, the need for high-quality and efficient AAV vector production will increase substantially over the next decade. The Viral Innovation Core (VIC) seeks to meet the AAV vector needs of the UMN addiction research community, providing Center Investigators and Affiliates with access to advanced and experimental AAV production services, as well as a rigorous set of quality control and product evaluation processes that will inform the optimal design of future AAV-based investigations. The mission of the VIC is encapsulated in two Specific Aims: 1) Generation and advanced characterization of AAV vectors. The VIC will support the generation of AAV vectors ? including custom vectors ? for the UMN addiction research community. The VIC will employ a stringent process of product evaluation and quality control that, in aggregate, will represent a comprehensive profile of virus quality that can be used to help optimize vector production and purification approaches. This effort, combined with application-specific feedback, will help the VIC best advise investigators on the design, use, and storage of these tools. Providing this labor-intensive service through a centralized entity with skilled staff represents a critical efficiency for the VIC user base, and will facilitate the centralized examination, evaluation, and interpretation of data from a large and broad array of vector tools. 2) Engineering tropism of AAV. The VIC will also direct a research and development (Special Projects) program with the goal of developing new methodologies to improve the delivery of AAV vectors, oriented around the specific needs of the UMN addiction research community. The VIC will investigate whether ?arming? tropism-null AAV vectors with antibodies or other non-immunoglobulin scaffolds can redefine their tropism in a user-specified manner. Engineered tropism, which will enable viral gene delivery based on one or more surface receptors or markers, would represent a powerful approach to achieving precise manipulation of neural circuits relevant to addiction. Summary/impact. Tools generated by the VIC will promote engagement with the Structural Circuits Core and Imaging Cells during Behavior Core, fueling insights that will be consolidated within the Addiction Connectome Core. The efforts of the VIC will also yield synergies that expand the scope of supported projects and increase the impact of UMN research in the area of addiction. Furthermore, new multi-modal AAV targeting paradigms will represent a substantial benefit to the broader internal and external neuroscience research communities.